Sir Kim said: “I have been 40 years in the foreign service, I’ve seen a number of presidents and Prime Ministers.

“There has never been a moment when the relationship hasn’t been really deep and strong, but also never a moment where there hasn’t been one or two issues on which we disagree.

“It’s a hugely strong relationship in lots of other areas – intelligence, security, trade, defence, and the trade relationship, 200 billion dollars-worth of trade both ways.

“And with Brexit and the potential for doing a free trade agreement between the UK and US, the future is going to be even bigger.”

Theresa May and Donald Trump during a meeting have met a number of times since his inauguration (Stefan Rousseau/PA)

Sir Kim was also quizzed on Iran – saying the UK agreed with the Trump administration that what the country was doing in the region was “unacceptable” – and the economy, where he admitted being “envious” of the recent success across the Atlantic.

On Brexit, presenter Bret Baier said there was a “lot of angst” about how Britain’s departure from the bloc would work, which was rebuffed by the ambassador.

Sir Kim said: “The next task is to agree transitional arrangements that will give certainty and continuity not just to British, but to international businesses present in the UK and beyond that we need to work out a future trading relationship with the EU.

“I am confident we will achieve all of that but I am also confident that we have this great opportunity then to forge stronger trading relationships with the rest of the world, free trade agreements, starting with here in the US.”